Preparation of artificial resin compression mixtures



Patented Feb. 23, 1937 UNITED STATES PATENT PREPARATION OF ARTIFICIALRESm OFFICE COM- 2 Claims.

It is known to prepare artificial resin compression mixtures, i. e.intimate mixtures of artificial resins, particularly soluble and fusiblecondensation products of phenols and formaldehyde, capable of beinghardened, and filling substances, particularly wood powder, byintimately mixing or kneading resols, either in liquid or finelypowdered condition, or in the form of an alcoholic solution, withfilling substances.

In the solvent-process the solvents are removed by heating and the solidmass compressed in a granulated or powdered form in known manner.Working with solvents has the disadvantage that these solventsadhereextremely fast to the mix-' ture and can only be expelled by longheating. This long heating, however, reduces the flowing properties ofthe finished compression mixtures to an extraordinary degree. On theother hand if this long heating is omitted the material, owing to'thoretention of the solvent in the compression mixture, can only becompressed with great difliculty, since vapours are given off andconsequently blisters form and it is therefore impossible to obtain highvalue compressed articles. The mixing process on rollers, on the otherhand, has the disadvantage that, on mixing the material together, afurther condensation of the resin also takes place at the same time,whereby it becomes extremely difiicult to hit the exact point when theproduct is homogeneously mixed and suflicient condensation has takenplace. In this case also it is extremely diflicult to obtain uniformcompression mixtures having 'the' desired flowing properties andpermanence of compression.

According to this invention it has been found that compression mixtures,which are precondensed to any desired degree and are also completelyhomogeneously mixed, can be prepared without difficulty by bringingtogether finely powdered, suitably precondensed resin and suit,- ablequantities of finely powdered filling material, if desired with theaddition of pigments and agents for preventing'adhesionto the matrices,intimately mixing the ingredients together in a suitable apparatusforexample a mill, and thereafter subjecting the mixture for a short timeat a high temperature to a high compression pressure, after which thepressure is rapidly released and the temperature lowered. This treatmenthas the purpose and effect of bringing the resin, owing to the hightemperature, into a liquidform and at the same time forcing the resininto the finest pores of the filling material owing to the high pressureproduced. This treatment can, for

In Germany March 27, 1930 example, becarried out by spreading out themixture in a thin layer on a plate, thereafter subjecting the mixture toa high pressure with the aid of a second plate, heating for a short timeand then rapidly cooling down the mixture, whilst releasing thepressure. The process may also be advantageously carried out by forcingthe above described mixture through nozzles heated to high temperatures.Uniform mixing and impregnation of the resin and the filling substancethereby takes place in the nozzle.

The conditions, according to which this treatment takes place, must beso chosen that fusion of the resin takes place in the entire layerwhilst the outer layers, by employing suitable temperatures, areprevented from passing over into the final condition, so that thematerial after impregnation can still be compressed in any desiredmanner.

As filling materials there may be employed wood powder, fibroussubstances of every kind, mineral filling substances, such as asbestos,talc, lithopone, magnesia, etc. I

are intimately mixed ina mill and the mixture rapidly forced throughnarrow nozzles of any desired shape and of suitable length heated toabout 200 C. After cooling the mixture may, if

desired, be powdered. y

What I claim is:

1. A process for preparing a consolidated com-' pression mixture whichis capable of pressmouldinginto shapes and hardening, and is of vuniform quality and comprises an artificial resin in resol formhomogeneously mixed with and impregnating a porous solid fillingmaterial, which comprises bringing together finely powdered precondensedresin in resol form with finely powdered porous filling materialin theabsence of resin solvent and thereby forming an intimate dry powderymixture, subjecting the mixture for a short'time to a high compressionpressure at a high temperature andthereby uniformly liquefying therennin the presence of the filling material so that the liquefied resinunder said pressure permeates and impregnates the pores of the filler,and rapidly cooling and releasing the presdry powdery mixture, forcingthe mixture uniformly and rapidly under high pressure through arestricted orifice while subjecting it to an elevated temperature foruniformly liquefying the resin in the presence of the filling materialso that the liquefied resin under said pressure permeates andimpregnates the pores of the filler, and rapidly cooling and effectingthe escape of the mixture from the pressure and temperature existing atthe orifice before a substantial conver- 19 sion and hardening of theresol has occurred.

' RICHARD HESSEN.

